CORRESPONDENCE: LETTER TO THE EDITOR
Reply
Shigeto Namiuchi, MD* and
Yutaka Kagaya, MD
* Department of Cardiology, Iwaki Kyoritsu General Hospital, Japan Department of Cardiovascular Medicine, Tohoku University Graduate School of Medicine, 1-1 Seiryo-machi, Aoba-ku, Sendai 980-8574, Japan (Email: kagaya{at}cardio.med.tohoku.ac.jp).
We appreciate the interest and thoughtful comments of Dr. Lipsic and colleagues regarding our study (1). The conclusions of our study were that a higher endogenous erythropoietin (EPO) level can predict a smaller infarct size in patients with acute myocardial infarction (MI) subjected to successful primary percutaneous coronary intervention (PCI), and that this might be attributed to the potentially protective effect of endogenous EPO against ischemia-reperfusion injury in humans. As pointed out by Dr. Lipsic and colleagues, these conclusions may be in contrast to those of studies by Dr. Lipsic and colleagues (2) and by others as well (3). They reported that a lower hemoglobin content was associated with higher mortality in patients with acute MI (2) and stable coronary artery disease (CAD) (3). We would like to emphasize, however, that in our study the hemoglobin concentration was not an independent predictor of the infarct size, whereas the endogenous EPO level was. We believe that we cannot directly compare the results of our study with those of the two studies by Dr. Lipsic and colleagues and by others because they did not measure the serum EPO level in their patients.
Dr. Lipsic and colleagues also reported that, in patients with chronic heart failure, elevated plasma EPO levels are associated with an impaired prognosis (4). The mechanisms of the increased plasma EPO levels in some patients with chronic heart failure are still unclear, and they may be different from those in the patients with acute MI in our study. As described in our report (1), it is possible that current smoking increased the hemoglobin content in the blood and affected the serum EPO levels of the patients in the low EPO group. With regard to the timing of the blood sampling for the serum EPO level, we collected the blood samples 9.9 ± 5.2 h after the onset of acute MI as described in the Methods section of our study. We believe that Dr. Lipsic and colleagues misunderstood this issue.
We agree with the investigators that a future study with a larger number of patients is needed to draw a more definitive conclusion regarding the role of endogenous EPO in acute MI.
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1. Namiuchi S, Kagaya Y, Ohta J, et al. High serum erythropoietin level is associated with smaller infarct size in patients with acute myocardial infarction who undergo successful primary percutaneous coronary intervention J Am Coll Cardiol 2005;45:1406-1412.[Abstract/Free Full Text]2. Lipsic E, van der Horst IC, Voors AA, et al. Hemoglobin levels and 30-day mortality in patients after myocardial infarction Int J Cardiol 2005;100:289-292.[CrossRef][Web of Science][Medline] 3. Reinecke H, Trey T, Wellmann J, et al. Haemoglobin-related mortality in patients undergoing percutaneous coronary interventions Eur Heart J 2003;24:2142-2150.[Abstract/Free Full Text] 4. van der Meer P, Voors AA, Lipsic E, et al. Prognostic value of plasma erythropoietin on mortality in patients with chronic heart failure J Am Coll Cardiol 2004;44:63-67.[Abstract/Free Full Text]
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